Horseshoe nail and horseshoe nail forming process

ABSTRACT

A nail for fixing a shoe to a hoof includes a head, and a shank extending from the head generally along a centerline and terminating in a tip. A reaction region is formed in the shank adjacent the tip and has a flattened profile having front and rear surfaces interconnected by respective edge surfaces. In the reaction region the front surface is convexly curved to incline the front surface relative to the centreline of tho shark The edge surfaces converge relative to each other towards the tip, whereby, on forcing the nail into the hoof, the reaction region is adapted to produce a resultant force on the nail. The resultant force is caused by engagement of the reaction with the hoof. The resultant force is adapted to predispose the nail to bend about the rear surface of the reaction region Also disclosed are processes for forming a horseshoe nail.

FIELD OF THE INVENTION

The present invention relates generally to nails of the kind useful forfixing a shoe to a hoof, and to methods for forming such nails. Nails ofthis kind are referred to herein as horseshoe nails.

BACKGROUND ART

Horseshoe nails are specifically designed to bend as they are driveninto a hoof. Typically a farrier drives the horseshoe nail into thebottom of the hoof through a slot in the shoe and as the nail is driveninto the hoof, it bends so that the tip is caused to pass out the sideof the hoof. Once in this position, the farrier removes the tip of thenail, either by cutting or ringing it off, and drives the remainingshank downwards against the hoof. This secures the nail, and thereforethe shoe, in place.

A typical horseshoe nail includes a shank of generally rectangular crosssection, and a head located at one end of the shank. The shank has afront and a rear surface interconnected by opposing edge surfaces, theedge surfaces being flat and nearly parallel but slightly tapered alonga major part of the shank. In the end quarter of the shank remote fromthe head the edge surfaces converge together to form the tip. The rearsurface of the shank is substantially flat, whereas the front surface ofthe shank is also flat along the major part of the shank except adjacentthe tip where the front surface is angled to converge towards the rearsurface at the tip. This angled portion is designed to cause the nail tobend as it is driven into the hoof.

It is desirable that the nail exit the hoof at a particular distancefrom the shoe. A well shot horse will have a ring of horseshoe nailsspaced around the hoof all exiting the hoof at approximately the samedistance from the bottom of the hoof. If a nail bends too sharply, itcan fracture off an edge of the hoof. If a nail does not bendsufficiently or bends the wrong way, it cannot be secured in place and,moreover, can lame the horse.

In analysing the way a horseshoe nail bends when it is being driven intoa hoof, it is considered that whilst the loading to cause bending isinitially induced on the angled portion or reaction region adjacent thetip, as the nail beings to bend this loading is transferred along theshank towards the head. As a result, the part of the shank which extendsfrom the angled portion towards the head is the main part of the nailwhich bends and throughout the specification, reference to the "bendingregion" of the nail refers to this part of the shank.

Horseshoe nails have generally been formed from a slug of metal cut fromwire or rod of a gauge similar to the intended mean diameter of the nailhead. This slug is drawn or rolled out, typically by air hammers, toform the head and to reduce its cross-section while forming thecharacteristic rectangular shank profile. To reduce work hardening, thenail undergoes one or two annealing treatments during or followingshaping. Once fully shaped, the shank is then sheared to form the tip.

A problem with previous horseshoe nails is that they do not bend in aconsistent manner. A broad reason is a lack of uniformity in thestructure and bending properties of the nails, despite a seeminglyuniform method of formation. One common cause of non-uniformity is thepresence of flaws formed in the nails during their manufacture. Theseflaws are a consequence of the complexity in the nail forming operationand are often present as surface defects, such as dimples, orinconsistencies within the microstructure of the nail. As a result ofthe flaws, the nails will often have a weakened area which may cause thenail to bend the wrong way, or, in the case of flaws occurring in themicrostructure, the nails may have an area of increased hardness in thenail shank which may cause the nail to drive straight or not bendsufficiently. Surface defects can have marked effects on the bendingperformance of the nail particularly when they are located in the tip orreaction region, whereas flaws in the microstructure cause particularproblems when they occur in the bending region of the shank.

While a farrier is able to detect surface defects on a visual inspectionof the nail, it is not practical for the farrier to examine the nail todetermine if there are flaws in the microstructure. Typically the onlyway the farrier detects these flaws in the microstructure is by the feelof the nail, in particular as the nail is being driven into the hoof andthis usually can only be done by experience farriers.

Another known cause of inconsistent bending is the presence of a regionof increased resistance within the hoof which causes the nail to bedeflected from its optimal path.

SUMMARY OF THE INVENTION--NAIL ASPECTS

An aim of the present invention is to provide an improved nail which issuitable for fixing a shoe to a hoof and an improved method of formingthe nail. A particular aim of the invention is to provide a horseshoenail which is able to bend more consistently.

In first and second aspects, the present invention provides a nail forfixing a shoe to a hoof, the nail including a head, and a shankextending from the head generally along a centreline and terminating ina tip. A reaction region is formed in the shank adjacent the tip, andhas a flattened profile having front and rear surfaces interconnected byrespective edge surfaces.

In the first aspect of the invention, in the reaction region, the frontsurface is convexly curved to incline the front surface relative to thecentreline of the shank, and the edge surfaces converge relative to eachother towards the tip, whereby, on forcing the nail into the hoof, thereaction region is adapted to produce a resultant force on the nailcaused by engagement of the reaction region with the hoof, the resultantforce being adapted to predispose the nail to bend about the rearsurface of the reaction region.

In the second aspect of the invention, which may be alternative to oradditional to the first aspect, the edge surfaces are convexly curvedtowards the tip in the reaction region so as to converge towards thetip, and the front surface in the reaction region is inclined relativeto the centreline of the shank. In prior art nails, the edge surfacesare typically straight or flat as they converge to the tip in thereaction region.

The advantage of convexly curved edge surfaces is that the tip is bettersupported than the prior art nails while still enabling the nail to bepredisposed to bend in a direction about the rear surface. As a resultof the tip being better supported, it is less likely to be damaged by animpacting force being applied to the tip. Therefore it is less likelythat flaws, such as dimples, are formed in the nail during itsmanufacture which could otherwise cause the nail to bend incorrectly inuse. Furthermore, with the tip being better supported, the nail is lesslikely to deviate from its path on striking a region of increasedresistance within the hoof.

A further advantage of having the edge surfaces of the reaction regionconvexly curved, is that the area of the front surface is increased ascompared to a straight edge surface. As the magnitude of the resultantforce produced by the reaction region is proportional to the size of thefront surface, this increases the resultant force produced on the nail.

Preferably, the reaction region merges with the remaining part of theshank such that the flattened profile extends towards the head. In thisway, at least the majority of the shank has front and rear surfaceswhich are interconnected by the edge surfaces.

In a third aspect, which may be alternative to or additional to thefirst and second aspects, the present invention is directed to providinga nail for fixing a shoe to a hoof which includes a predeterminedvariation in the microstructure of the nail to predispose the nail tobend in a desired orientation. Accordingly, this aspect of the inventionhas particular application to horseshoe nails with the predeterminedvariation in microstructure being designed to facilitate bending of theshank about the rear surface.

In one form of the third aspect of the invention, the microstructure mayexhibit a predominantly uniform grain structure with the variation beingin the degree of elongation of the grain structure. In another form, themicrostructure may exhibit variations in the mechanical properties ofthe microstructure. For example, the hardness may vary in differentregions of the shank. This variation in the mechanical properties of themicrostructure may be due to a variation in the type of grain structureor, as in the above case wherein a predominantly uniform grain structureis provided, by a variation in the orientation or elongation of thegrain structure.

Variations in the microstructure have occurred in previous horseshoenails mainly as a result of the forming process. However, previouslythese variations have randomly occurred throughout the nail structureand as mentioned above, have resulted in inconsistency in the bendingperformance of the nail. In contrast, in the third aspect of the presentinvention, these variations are not random throughout the nail structurebut rather are specifically incorporated to predispose the nail to bendin a desired orientation. The advantage of this arrangement is that itcan improve the bending performance of the nail. Further it isconsidered that this improvement in performance results in part from thepredetermined variation in the microstructure offsetting any randomvariations in the microstructure which may occur during the complexforming process.

A nail for fixing a shoe to a hoof provided in accordance with the thirdaspect of the invention includes a head, and a shank extending from thehead along a longitudinal axis and terminating in a tip. The shank has aflattened profile having front and rear surfaces interconnected byrespective edge surfaces. The shank includes a reaction region adjacentthe tip and a bending region intermediate the reaction region and thehead. The shank including the bending region exhibits a predeterminedvariation in microstructure so as to produce, on forcing the nail into ahoof, a resultant force adapted to predispose the nail to bend at thebending region about the rear surface of the shank.

In one form of the third aspect, the invention is characterised in thatthe variation in the microstructure occurs at the bending region withthe microstructure at the region of the front surface differing from themicrostructure at the region of the rear surface of the shank.

In one form, the microstructure at the bending region along a crosssection normal to the longitudinal axis of the shank exhibits apredominantly uniform grain structure having a greater degree ofelongation of the structure at the front surface than at the rearsurface. In one form, the degree of elongation of the grain structuregenerally decreases from the front surface to the rear surface.

In another form, the microstructure at the above cross section ischaracterised by a variation in the mechanical properties of thestructure between the front surface and the rear surface. In one form,the hardness of the structure in the region of the front surface isgreater than the hardness in the region of the rear surface. In oneform, the hardness of the structure generally decreases from the frontsurface to the rear surface.

In one form, the microstructure at the front surface exhibits a hardnesswhich is in the range of 10 to 50%, more preferably 20 to 40%, greaterthan the hardness of the microstructure at the back surface.

The abovementioned variations in the microstructure in the shank betweenthe front surface and the rear surface are considered to improve thebending performance of the nail. On driving the nail into a hoof, theloading acting along the axis of the shank causes the softer or moreductile portions of the shank at the rear surface to deform before theharder front surface. This deformation draws the nail to bend about therear surface and complements the action of the resultant force acting atthe reaction region. It is further considered that the harder region atthe front surface provides a support for the nail shank and preventsnail collapse, which therefore assists in maintaining the nail on itsoptimum path as it bends through the hoof.

In another form of the third aspect, the invention is characterised inthat the variation in the microstructure occurs between the reactionregion and the bending region. In one form the shank exhibits amicrostructure and predominantly uniform grain structure and, in a crosssection along the longitudinal axis, the microstructure exhibits agreater degree of elongation of the grain structure in the reactionregion than in the bending region.

In one form, in the cross section along the longitudinal axis, thevariation in the microstructure is characterised by a variation in themechanical properties of the structure. In one form, in the crosssection along the longitudinal axis, the hardness in the reaction regionis greater than the hardness in the bending region.

It is considered that this variation between the reaction region and thebending region improves the bending performance of the nail. Thevariation of the microstructure between the reaction region and thebending region makes it less likely that the reaction region willexcessively bend on forcing the nail into the hoof. In this way thereaction region is better able to support the tip of the nail. As aresult of the tip being better supported, it is less likely to deviatefrom its optimum path of travel through the hoof.

Preferably, in all three aspects of the invention thus far disclosed, atleast part of the edges between the front surface and the adjacent edgesurfaces of the shank are chamfered. Preferably the chamfer on each edgedoes not extend through the reaction region. This arrangement has theadvantage that the front surface of the reaction region is not reducedby the chamfer which in turn enables the magnitude of the resultantforce produced by the reaction region to be maximised.

Preferably the nail has a generally tapered appearance with the frontand rear surfaces as well as the edge surfaces tapering towards the tip.Preferably, the front surface converges towards the centreline of theshank whilst the rear surface, which is substantially flat, remainsparallel to the centreline. Preferably, both the edge surfaces convergetowards the centreline.

Preferably the head is larger than the shank and is generallyrectangular in cross section having a front and rear surfaceinterconnected by edge surfaces, and includes a flattened top or endbearing surface. Preferably the rear surface of the head issubstantially flush with the rear surface of the shank whereas the edgesurfaces and the front surface diverge outwardly from the shank.

The amount of bending of the nail in use depends on the magnitude of theresultant force, the dimensions of the nail, and the strength of thematerial from which the nail is made. Accordingly, the dimensions of thenail, such as its thickness, length and the amount of curve on the frontsurface of the reaction region in the first aspect of the invention, aswell as the material from which the nail is made, may vary depending onthe type of hoof in which the nail is to be used as well as the amountof bend that is desired. For a particular application of the nail, theserequired parameters can be determined through trial and experiment by aperson skilled in the art. Further, the construction of the reactionregion can be incorporated, and the benefits realised, in thesedifferent nail constructions. Therefore, to gain an understanding of theinvention it is not necessary to specify these parameters in any detail.

SUMMARY OF THE INVENTION--PROCESS ASPECTS

In fourth and fifth aspects of the invention, a method of forming a nailis provided. In the fourth aspect, a method of the invention is adaptedto incorporate the variations in the microstructure of the nail which isthe subject of the third aspect of the invention. In this fourth aspectof the invention, a nail is formed from a feed material of predominantlyuniform grain structure and the desired variation in the microstructureis provided by regulating the amount of cold working the nail issubjected to during the forming process.

Accordingly, in its fourth aspect, the present invention provides amethod of forming a nail for fixing a shoe to a hoof, the nail having ahead, and a shank extending along a longitudinal axis from the head andterminating in a tip, the shank having a flattened profile having frontand rear surfaces, and the method including the steps of:

(i) providing a nail blank formed from feed material having apredominantly uniform grain structure; and

(ii) forming the flattened profile of the shank by cold working the nailblank with a front surface of the shank being subjected to a greaterdegree of cold working than a rear surface of the shank.

In one form, the flattened profile of the shank is formed by coldworking the nail blank in a direction substantially transverse to thelongitudinal axis. In one form, the nail blank is located betweencooperating dies and the shank is cold worked by a pressing operation.In one form, the nail blank is located on one of the dies and, duringthe pressing operation, the other die is moved into engagement with thenail blank. In this arrangement, the rear surface of the shank is formedagainst the one die and the front surface is formed against the otherdie.

In one form, the sides of the nail blank interconnecting the front andrear surfaces are not constrained during the pressing operation. In thisway, elongation of the nail blank in a direction outwardly from thelongitudinal axis is facilitated. In one form, to increase the variationin cold working between the front and rear surfaces and to facilitatethe elongation of the blank outwardly from the longitudinal axis, atleast one of the cooperating dies includes a recess which extendsgenerally parallel to the longitudinal axis of the shank. During thepressing operation, the feed tends to flow into this recess. Preferablythe one die includes a pair of these recesses located on opposing sidesof the blank. In this arrangement, the forming of the shank includes afurther step of shearing the blank in the direction of the longitudinalaxis to remove the metal which has flowed into the recesses and to formthe opposing side surfaces of the shank which interconnect the front andrear surfaces.

The advantage of this arrangement is that varying the amount of coldworking between the front and rear surfaces causes a correspondingvariation in the microstructure. More specifically, the degree ofelongation of the grain structure decreases from the front surfacetowards the rear surface. This results in a variation in the mechanicalproperties of the nail, such as its hardness.

Particular advantages are achieved by providing the recesses on the onedie. It is considered that this arrangement increases the amount ofvariation in the cold working between the front and rear surfaces.During the pressing operation, the material is caused to flow from thecontact area of the other die and moves into the recesses. This actioncauses additional working in the area of the nail blank contacting theother die than in the area of contact at the one die where the materialremains fairly stationary. This in turn results in a greater degree ofwork hardening being formed at the front surface than at the rearsurface.

A further advantage is that the most heavily worked sections of theblank are removed. These sections are the side parts which form in therecess. The advantage of this arrangement is that the more heavilyworked areas are more likely to include flaws in the microstructurewhich may otherwise cause problems with the bending performance of thenail.

Also in its fourth aspect, the present invention provides a method offorming a nail for fixing a shoe to the hoof, the nail having a head,and a shank extending along a longitudinal axis from the head andterminating in a tip, the shank including a reaction region adjacent thetip and a bending region intermediate the reaction region and the head,the reaction region being shaped so as to produce, on forcing the nailinto the hoof, a resultant force adapted to bias or predispose a nail tobend at the bending region in a desired orientation, the methodincluding the steps of:

(i) providing a nail blank formed from feed material having apredominantly uniform grain structure; and

(ii) forming the shank by cold working the nail blank with the reactionregion being subjected to a greater degree of cold working than thebending region of the shank.

The advantage of this aspect of the invention is that varying the amountof cold working between the bending region and the reaction region ofthe shank causes a corresponding variation in the microstructure. Morespecifically, the reaction region exhibits a microstructure having agreater degree of elongation of the grain structure than themicrostructure in the bending region. This results in a variation inmechanical properties, such as the hardness, between the reaction regionand the bending region.

Still further in its fourth aspect, the present invention provides amethod of forming a nail for fixing a shoe to a hoof, the nail having ahead, and a shank extending from the head generally along a longitudinalaxis and terminating in a tip, the shank of said nail having apredetermined range of hardness along the shank and the method includingthe steps of:

(i) providing a nail blank formed from a feed material having a hardnesswhich is less than said predetermined range of hardness;

(ii) forming the shank by cold working the nail blank;

(iii) controlling the cold working of the blank so as to increase thehardness along said shank to within said predetermined range ofhardness; and

(iv) shearing said shank so as to form said tip.

The advantage of this aspect of the invention is that the hardness inthe shank is controlled in the forming process. The expected increasedin hardness in cold working the nail blank is factored in by preferablychoosing a wire feed having a hardness which is significantly less thanthe final desired range of hardness, and by controlling the cold workingof the shank so that the increase in hardness caused by this processstep equals the amount required to attain the desired hardness at aparticular point on the shank. In one form, the hardness of the shankvaries along the length of the shank and, preferably, the hardness ofthe tip region is greater than other parts of the shank. In one form,the hardness of the shank varies between the front and back surfaces,and in particular the hardness decreases from the front surface to therear surface. In one form of the invention, the variation in hardness isachieved by varying the degree of cold working along the shank.

This fourth aspect of the invention provides significant advantages. Inprevious methods of forming horseshoe nails, the nail is required toundergo an annealing step before final forming of the nail to reduce thework hardening which has occurred in the earlier stages of nailformation. By incorporating the annealing step in this previous nailformation process, the control of the microstructure of the nail isdiminished as the annealing step can result in irregular grain structureforming within the microstructure. An advantage of the fourth aspect ofthe invention is that by creating a situation where this annealing stepis not required, the microstructure of the nail is further controlled.Furthermore, variations in the microstructure may be arranged to beincorporated in the forming process. In particular, it is possible todesign a nail formed from a predominantly uniform feed material whichexhibits a variation in the amount of elongation of the grain structureso as to exhibit a variation in hardness at different regions along theshank. In particular, it is possible to provide a nail which exhibits avariation in hardness between the front and rear surfaces and avariation in hardness between the bending region and the reactionregion. This variation in hardness is considered ideal. In addition, theforming operation is simplified.

In one form, the reaction region is subjected to a higher degree of coldworking as compared to the other parts of the shank. This gives thereaction region a higher degree of grain elongation and hardness. Whilethe additional cold working may produce local variation in themicrostructure of the tip region of the shank, this variation does notcause the nail to bend inconsistently as the majority of the bendingoccurs in the bending region of the shank. In contrast as mentionedabove, it is considered that this variation improves the bendingperformance as the increase in the hardness of the reaction regionfurther supports the tip of the nail.

Preferably after cold working the reaction region, the nail undergoes ashearing step to form the tip. In one form this shearing step also formsthe opposing edges of the reaction region. In one form, the reactionregion is formed with the front surface incorporating the angled portionbeing generally curved and the opposing edge surfaces being convexlycurved and being arranged to converge relative to each other towards thetip.

In one form, the feed material is wire. In one form, the wire feed hasbeen produced using a suitable heat treatment process resulting in theformation of a predominantly uniform, equiaxed or elongated, ferritestructure. The form of the carbide present in the structure may beeither spheroidal or lamellar. The hardness of the wire feed prior tothe initial cold working operation is preferably less than 200 HV30.

The wire production process can involve a skin or sizing pass followingthe heat treatment operation and prior to the formation of the nailblank. The use of a suitably heat treated wire feed is preferred overother types of feed such as non heat treated drawn wire feed as themicrostructure and hardness of a heat treated wire is more consistent,thereby promoting a more uniform response to subsequent cold workingoperations.

Preferably, and according to a fifth aspect of the invention, the nailis formed by a method including the steps of:

(i) providing wire of a cross section of similar area to the subsequentshank;

(ii) upsetting an end of the wire to form the head; and

(iii) working a nail blank cut from the wire and including the head,substantially without drawing the blank, to form the flattened profileof the shank, and forming the tip on the flattened shank.

In this way, the conventional practice in horseshoe nail manufacture ofutilising a wire blank of gauge similar to the head, and the consequentdrawing operation, are avoided. In turn, the lack of drawing allows theannealing steps to be omitted, with consequent enhanced hardness at thetip, as well as the economic advantage of a simpler formation process.

The arrangement of the fifth aspect of the invention is also preferredas the upsetting operation increases the hardness of the shank adjacentthe head. This is beneficial as this area of the shank is under heavyloading in use and is prone to wear because it rubs against thehorseshoe. Furthermore as this region of the shank does not bend, theincrease in hardness does not effect the bending performance of thenail.

A further aspect of the invention provides a nail for fixing a shoe to ahoof which is formed by a method of any of the forms of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is an enlarged perspective view of a horseshoe nail according toa first embodiment of the invention, incorporating preferred features ofthe first, second and third aspects of the invention and made bypreferred steps of the fourth and fifth aspects of the invention;

FIGS. 2 to 4 are correspondingly enlarged plan, underneath and sideelevation views respectively of the nail shown in FIG. 1;

FIGS. 5 to 8 are schematic views of successive operations of anapparatus for forming a head on a nail blank to be further formed into anail such as that shown in FIGS. 1 to 4;

FIG. 9 is an exploded perspective view of an apparatus for forminghorseshoe nails from headed blanks produced by the apparatus depicted inFIGS. 5 to 8;

FIGS. 10 to 16 are respective views to an enlarged scale of nail blanksformed at different stages of the apparatus of FIG. 9;

FIGS. 17 to 19 are schematic cross sections illustrating how thehorseshoe nail bends as it is driven through a horse's hoof; and

FIG. 20 is a photomicrograph of a cross section of the nail depicted inFIGS. 1 to 4, approximately on the line X--X in FIG. 3, and produced bythe apparatus of FIG. 9.

DESCRIPTION OF PREFERRED EMBODIMENTS

The horseshoe nail 10 illustrated in FIGS. 1 to 4 is formed from fullyannealed steel wire having a predominantly uniform grain structure, suchas that sold by The Broken Hill Proprietary Company Limited (BIP) underthe trade name SOFI DRAWN XU1004, by the method to be described belowwith reference to FIGS. 5 to 16. Nail 10 has a head 11 and a shank 12extending from the head and terminating in a tip 13.

The nail 10 has a generally rectangular cross section relative to acentreline or longitudinal axis 14 extending along the shank 12, with afront surface 15 and a rear surface 16 interconnected by opposing edgesurfaces 17,18. The head 11 is larger than the shank and has a rearsurface 19 which is substantially flush with the rear surface 16 of theshank, a front surface 20, and opposing edge surfaces 22, which divergeoutwardly from the shank 12. A flat bearing surface 23 is formed at thetop or end of the head 11.

The nail has a generally tapered appearance, with the front and rearsurfaces 15,16 of the shank, as well as the edge surfaces 17,18,tapering towards the tip. The front surface 15 converges towards thecentreline 14 of the shank whilst the rear surface 16, which issubstantially flat, remains parallel to the centreline 14. Both the edgesurfaces 17,18 of the shank converge towards the centreline.

A reaction region 24 is formed in the shank 12 adjacent the tip 13. Theregion has a front surface 25, a rear surface 26 and opposing edgesurfaces 27,28 each of which is a continuation of a correspondingsurface of the shank. The front surface 25 and the opposing edgesurfaces 27,28 are arcuate and convexly curve relative to the centreline14 to the tip 13. The rear surface 26 is substantially flat and remainsgenerally parallel to the centreline 14.

Respective chamfers 29,30 are formed on the comer edges between thefront surface 15 and the adjacent edge surfaces 17,18. The chamfer oneach edge extends along the majority of the shank 12 but does not extendthrough the reaction region 24. Shoulders 31,32 are formed at thetermination of the chamfers 29,30 adjacent the reaction region 24.

Nail 19 is formed from wire of a cross section of similar area to thecross section of shank 12, and length slightly greater than the lengthof the final nail. The first step is to upset an end of the wire to formthe head and so form the segment into a nail blank. A suitable apparatus40 for forming such nail blanks is schematically illustrated in FIGS. 5to 8.

The apparatus 40 includes a clamp 41 and hammer 42. The wire is firstlycut and placed into the clamp 41 (FIG. 5). The clamp 41 includes arecess 43 in an upper surface 44 which is adapted to cooperate with thehammer 42. The cut wire feed 50 is clamped with an end region 51projecting from the upper surface 44.

The hammer 42 includes a plunger 47 in a bore 47a which widens into arecess 45 in lower surface 46, and is adapted to engage the clamp 41 sothat the end region 51 of the wire feed 50 is received through recess 45into bore 47a, with the recesses 43,45 in register (FIG. 6).

To carry out the upsetting operation, which forms a head 52 on the wirefeed 50, plunger 47 of the hammer 42 is driven onto the end of the wirefeed 50 as illustrated in FIG. 8, causing the end region 51 of the wirefeed to flow into recesses 43,45 and form a head 52 which issubstantially spherical. The wire feed is now cut and a headed nailblank 50' (FIG. 10) is recovered from the head forming apparatus. Theremay or may not be a residual tail 50a. These nail blanks 50' aredelivered for further processing to the forming apparatus 60 illustratedin FIG. 9.

Forming apparatus 70 includes a plurality of cooperating dies (71a, 71b,72a, 72b, 73a, 73b, 74a, 74b, 75a, 75b, 76a, 76b, 77a, 77b). The diesare arranged in pairs, with a respective one of each pair being locatedin an upper annual die block 78 and the other die of each pair beinglocated in a matching annular lower die block 79. The die blocks areoperable under a hydraulic ram (not shown) with the dies being arrangedin a circular array around a central axis 80. However, it is to beunderstood that the respective pairs of dies could be configured andoperable under a different arrangement. In particular the dies could bealigned in a linear or other non-circular array and each or some ofrespective pairs of dies could be operable under a separate drivearrangement.

In the illustrated arrangement, an annular nail blank carriage 81, islocated between the upper and lower die blocks (78,79) and is moveableabout the central axis 80 of the forming apparatus 70. The carriage 81retains nail blanks 50' and is operable on release of pressure from therespective die blocks to move each nail blank through each of therespective pairs of dies to enable the nail blanks 50' to be formed byeach of the respective dies.

The apparatus 70 further includes a feed arrangement to enable the nailblanks 50' to be fed onto the nail blank carriage 81. The feedarrangement is not shown in the illustration but is adapted to feednails through an arcuate recess 82 in the upper die block 78. The blanksare delivered from the feed arrangement onto an upstanding plate or land83 located on the lower die block and which is adapted to be alignedwith the nail blank carriage 81.

With reference to FIG. 9 and to FIGS. 10 to 16, each nail blank 50'undergoes six forming steps within the forming apparatus 70 under thevarious cooperating dies.

In a first step, the nail blank 50' (FIG. 10) is brought between dies71a,71b. These dies are adapted to cold work the nail blank 50' to shapethe head 52 and the top of the shank 53. The top die 71a includes arecess 84 in which the nail blank 50' is located. An elongate projection85 on the bottom die 71b is adapted to engage the opposing side of thenail blank 50'. On cooperation of the dies, the nail blank 50' is coldworked to shape the head 52 such that it has a pentagonal section oftapered thickness, and to also shape the top part of the shank 53 into agenerally rectangular section 53a (FIG. 11).

The second step is when the nail blank 50' is brought between dies72a,72b. This step is adapted to commence forming the balance of theshank 53, by flattening the shank 53. The upper die 72a incorporates atapered channel 86 which is adapted to receive the nail blank 50'. Thelower die 72b includes a central support 87 bordered by a pair ofchannels 88,89. The opposing side of the nail blank 50' is supported onthis central support 87. On cooperation of the dies, the balance of theshank 53 is flattened with excess material flowing into the recesses88,89. This gives the shank 53 a channelled profile (FIG. 12) having aweb 54 extending between opposing flanges 55,56 which tapers inthickness from the base of the head to the end of the shank. Thisprocess of material flow into the recesses causes the area 61 of thenail blank in contact with upper die 72a to be cold worked to a greaterextent than the area 62 of the nail blank in contact with the lower die72b. It is believed that this difference is due to the significantlygreater material flow around the outside of the U-shape into recesses88,89 than on the inside against the lower die. The outcome in the finalnail is a variation of cold working between the front surface 15 and therear surface 16 of the finished nail.

In the next step, the major part of the shank 53 is shaped by a shearingoperation which removes the flanges 55 and 56 to leave the web 54. Inthis step, the nail blank 50' is brought into engagement with the dies73a,73b. Shearing blades 90 form the top die 73a which are cooperablewith opposing edges of a support plate 91 formed on the bottom die 73b.During this shearing step, the flanges 55 and 56 are removed withopposing sides 57 and 58 of the shank 53 being formed at the shear line.The shank 53 is sheared such that it tapers in width from the tiptowards the head (FIG. 13).

The next step is a further cold working step which commences formationof the reaction region 24 adjacent tip 13 of the nail 10 and furtherworks the major part of the shank. In this step, the nail blank islocated between the dies 74a,74b. The upper die 74a includes a recess 92in which the shank 53 is located. The lower die 74b includes a plate 93.In this step, the tip region of the blank 50' is heavily cold worked toform the reaction region 59 in the shank 53 with the front surface 61aof the shank at the reaction region 59 being convexly curved (FIG. 14).The rear surface 62 of the shank remains substantially flat. Chamfers 63and 64 are pressed into the shank 53 on the front surface 61 tofacilitate passage of the nail 10 through a hoof. This step of theforming process causes the reaction region to be harder than theremaining shank.

The next step is a further shearing step where the formation of thereaction region 24 and tip 13 is completed. In this step, the blank 50'is located between dies 75a,75b. Similar to dies 73a,73b, the upper die75a includes shearing blades 94 which cooperate with opposing edges of asupport plate 95 located on the lower die 75b. In this step, theopposing edge surfaces 27,28 of the reaction region 24/59 are formed. Inthe illustrated form, the shearing blades 94 and support plate 95 areadapted to shear along an arcuate line such that the reaction regionedge surfaces 27,28 are convexly curved and merge towards the tip 13 ofthe blank 50' (FIG. 15).

The final forming step (FIG. 16) is to correct the flatness of the rearsurface of the shank and stamp a marking 67 into the head. This isachieved by cooperation of the dies 76a,76b.

The formed nail 10 is then located between dies 77a,77b, which arecooperable to force the nail out of the nail carriage 81. The nail 10passes into a recess 96 which is formed on the lower die 77b, wherein itpasses out from the apparatus 70. Once the nails 10 are ejected from theapparatus 70, they can if required be rumbled to improve their surfacefinish.

The benefits of this method of nail formation described above is thatthe increase in hardness of the nail can be controlled throughout theforming operation by controlling the amount of cold working the nail issubjected to. Furthermore the nail is able to exhibit a predeterminedvariation in the microstructure by varying the amount of cold working indifferent regions of the shank. By controlling these aspects of themicrostructure of the nail, an improved horseshoe nail is able to beformed which is able to bend more consistently than previous horseshoenails.

However it is to be realised that the amount of bending of the nail inuse depends on the magnitude of the resultant force on the nail, thedimensions of the nail, and the strength and material from which thenail is made. Accordingly, the dimensions of the nail, such as itsthickness, length and the amount of curve on the front surface of thereaction region, as well as the material from which the nail is made,may vary depending on the type of hoof in which the nail is to be usedas well as the amount of bend that is desired. For a particularapplication of the nail, these parameters will vary. However, thefeatures of the nail and the forming process described above can beincorporated, and the benefits realised, in these different nailconstructions.

The nail 10 is adapted to be hammered into a horse's hoof. The chamferededges 29,30, are adapted to facilitate passage of the nail through thehoof and reaction region 24 is adapted to produce a resultant force onthe nail caused by engagement of the reaction region with the hoof,which biases or predisposes the bending region 33 of the nail to bendabout the rear surface 16. The variation in the microstructure of thenail assists this process with the variation between the front and rearsurfaces being adapted to complement the resultant force acting at thereaction region, and the variation between the reaction region and thebending region assisting in supporting the tip. This operation isillustrated in FIGS. 17 to 19.

As illustrated in FIG. 17, the nail 10 is adapted to be hammered throughthe shoe 110 into the hoof 100 with the centreline 14 of the nail beinginitially substantially parallel to the respective side face 102 of thehoof. The nail is positioned through the pre-made slot 111 in the shoe,with the rear surface 16 facing outwardly. As the nail is hammered intothe centre of the wall or nail 105 of the hoof, and therefore initiallymidway between the interior 106 and the outer side surface 102, aloading is imparted to the front surface 25 of the interior of thereaction region 24. As this surface 25 is inclined to the centreline 14of the shank, it imparts a biasing force onto the nail, which biases thenail about the rear surface 16. Predisposal to bend about surface 16 ina consistent and predictable manner is further enhanced by the convexcurvature of surface 25. Furthermore, the loading on the nail whichextends along the shank causes the softer or more ductile portions ofthe shank at the rear surface 16 to deform before the harder frontsurface 15. This deformation draws the nail to bend about the rearsurface 16 and complement the action of the biasing force acting at thefront surface 25 of the reaction region 24 (FIG. 18).

The edge surfaces 27,28 of the reaction region 24 are convexly curvedand support the tip 13 and guide the tip 13 through the hoof as the nailbends about the rear surface 16. As the reaction region is harder thanthe bending region, the tip 13 remains well supported. Furthermore theharder region at the front surface of the nail shank assists inmaintaining the nail on its optimum path as it bends through the wall105 of the hoof, as it prevents the, nail collapsing or deflecting fromthis optimum path. As the nail curves into the harder outer zone of wall105, the radius of curvature increases. On fully driving the nail intothe hoof the tip 13 exits the side face 102 of the hoof (FIG. 19). Oncein this position, the tip 13 is removed and the remaining shank isdriven downwardly against the side face of the hoof which secures thenail, and therefore the shoe, in place. It is found that the nail of theembodiment also exits at an angle within a confined range, e.g. 30° to400 to side face 102, which is preferred for bending over.

Consequently, the nail 10 is predisposed to bend about the rear surfaceof the shank,. due to the shape of the nail as well as the variationwithin the microstructure. With this arrangement, the nail is lesslikely than the prior art horseshoe nails to deviate from its desiredcurved path on driving the nail into the hoof. Further the shape andhardness of the reaction region with the arcuate front and opposing edgesurfaces provide a more sturdy arrangement than prior art horseshoenails and is less likely to be affected by impact loading which mayoccur during manufacture or transportation of the nails.

An example of a horseshoe nail formed by the above method is describedbelow and a cross section depicting its microstructure is shown in FIG.20.

EXAMPLE

The feed material was an aluminium killed heat treated wire sold by BHPunder the trade name SOFT DRAWN XU1004. The wire had a tensile strengthof approximately 350 MPa and a diameter of 3.55 mm. The hardness of thefeed wire was approximately 120 HV30. The composition of the wire was asfollows:

    ______________________________________                                        C     P      Mn       Si   S     Cu   N     Ni  Al                            ______________________________________                                        0.06* 0.25*  0.25/0.40                                                                              0.05*                                                                              0.025*                                                                              0.05*                                                                              0.008*                                                                              --  0.025                         ______________________________________                                         *indicates maximum value.                                                

Following the initial upsetting operation, the nail blank had aspherical head of approximately 5.2 mm in diameter and 4.3 mm inthickness. The length of the headed blank was 47 mm.

On cold forming the head and the top of the shank under operation ofdies 71a,71b, the dimensions of the nail blank were as follows:

Head thickness--top 4.7 mm;

Shank--3 mm;

Head width, widest point 6.8 mm--top 4.5 mm--shank 3.8 mm;

The head height 5.9 mm--shank thickness 2.5 mm at base of head taperingto 2.1 mm adjacent to the original wire section;

Formed shank length 7 mm;

Total length of the headed blank 48 mm.

On flattening the remainder of the original wire section under operationof dies 72a,72b, the web of the shank was tapered in thickness from 3 mmat the base of the head to 1 mm at the end of the shank. The totallength of the headed blank was 49 mm.

On shearing the shank under operation of the dies 73a,73b, the thicknessof the shank was unchanged and the width of the shank tapered from 3.8mm at the base of the head to 2 mm at the tip of the blank. The totallength of the headed blank was 49 mm.

In the formation of the reaction region under operation of dies 74a,74b,the reaction region extended over 7 mm, with the thickness of the shankat the reaction region being reduced from 1 mm to 0.7 mm. The length ofthe total headed blank remained at 49 mm.

On shearing of the reaction region under operation of dies 75a,75b, thereaction region was tapered over the 7 mm length from the tip with themaximum width of the reaction region at the top being 2.4 mm. The totallength of the headed blank was 48 mm.

On flattening of the nail under operation of dies 76a,76b, the totallength of the headed blank was extended to 49 mm.

Table 1 indicates the hardness along a longitudinal cross section ofnail blanks after various stages of the forming operation.

Table 2 indicates the hardness of the finished nail at the bendingregion with tests being taken along a longitudinal cross section atpoints between the front surface and the rear surface.

Table 3 indicates the hardness of the finished nail at the reactionregion with tests being taken along a longitudinal cross section atpoints midway between the front and rear surfaces.

FIG. 20 is a photomicrograph of a representative cross section of thebending region of the finished nail, taken at approximately the lineX--X in FIG. 3. The photomicrograph illustrates the variation in theelongation of the grain structure between the front surface 15 and rearsurface 16. As clearly illustrated, the grain structure in the region ofthe rear surface is quite equiaxed but becomes more elongated towardsthe front surface. One of the hardness traverses detailed in Table 2 isalso illustrated with the references to five test points illustratedcorresponding to the references given in this table.

                  TABLE I                                                         ______________________________________                                        Hardness Test Results (HV30)                                                           Head-   Position-Shank                                                                            Bending Region                                   Section    1      2      3     4     5                                        ______________________________________                                        Original nail blank                                                                      164    202    124   118                                            After Operation of                                                                       216    159    177   118                                            Dies 11a, 11b                                                                 After Operation of                                                                       227    163    191   191                                            Dies 12a, 12b                                                                 After Operation of                                                                       216    156    172   147                                            Dies 13a, 13b                                                                 After Operation of                                                                       217    152    191   197   206                                      Dies 14a, 14b                                                                 After Operation of                                                                       215    151    189   189   209                                      Dies 15a, 15b                                                                 After Operation of                                                                       193    164    181   201   207                                      Dies 16a, 16b                                                                 ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Micro Hardness Test Results (MHV)                                             Rear Surface  Position-Bending Region                                                                       Front Surface                                   Traverse                                                                              1      2      3       4       5                                       ______________________________________                                        1       165.1  189.3  194.8   226.4   208.5                                   2       164.3  170.9  211.6   210.6   215.3                                   3       162.0  177.9  188.3   217.8   208.8                                   4       160.4  189.9  203.6   204.6   221.9                                   ______________________________________                                         Test Conditions                                                               Peak force  150 p                                                             Dwell Time  15 seconds                                                        Slope  20 p/s                                                            

                  TABLE 3                                                         ______________________________________                                        Micro Hardness Results (MHV)                                                  Tip End  Position - Reaction Region                                                                    Bending Region End                                   ______________________________________                                         1        2               3                                                   241      234             225                                                  ______________________________________                                         Test Conditions                                                               Peak force  150 p                                                             Dwell Time  15 seconds                                                        Slope  20 p/s                                                            

I claim:
 1. A nail for fixing a shoe to a hoof, the nail including ahead, and a shank extending from the head along a longitudinal axis andterminating in a tip, the shank having a flattened profile having spacedfront and rear surfaces interconnected by respective edge surfaces,wherein the shank includes a reaction region adjacent the tip and abending region intermediate the reaction region and the head, andwherein the shank at the bending region exhibits a predeterminedvariation in microstructure with the microstructure at the region of thefront surface differing from the microstructure at the region of therear surface of the shank, so as to produce, on forcing the nail into ahoof, a resultant force adapted to predispose the nail to bend at thebending region about the rear surface of the shank.
 2. A nail accordingto claim 1 wherein the microstructure at the bending region along across section normal to the centreline or longitudinal axis of the shankexhibits a predominately uniform grain structure having a greater degreeof elongation of the structure at the front surface than at the rearsurface.
 3. A nail according to claim 1 wherein the microstructure alonga cross section normal to the centreline or longitudinal axis of theshank is characterised by a variation in the mechanical properties ofthe structure between the front surface and the rear surface.
 4. A nailaccording to claim 3 wherein the hardness of the structure in the regionof the front surface is greater than the hardness in the region of therear surface.
 5. A nail according to claim 4 wherein the microstructureat the front surface exhibits; a hardness which is in the range of 10 to50% greater than the hardness of the microstructure at the rear surface.6. A nail according to claim 1 wherein at least part of respective edgesbetween the front surface and the adjacent edge surfaces of the shankare chamfered.
 7. A nail according to claim 6 wherein the chamfer oneach edge does not extend through the reaction region.
 8. A nailaccording to claim 1 wherein the nail has a generally tapered appearancewith the front and rear surfaces as well as the edge surfaces taperingtowards the tip.
 9. A nail according to claim 8 wherein the frontsurface converges towards the centreline or longitudinal axis of theshank, the rear surface, which is substantially flat, remains parallelto the centreline or axis, and both the edge surfaces converge towardsthe centreline or axis.
 10. A nail according to claim 1 wherein the headis larger than the shank and is generally rectangular in cross sectionhaving a front and rear surface interconnected by edge surfaces, andincludes a flattened top or end bearing surface.
 11. A nail according toclaim 1, wherein, in the reaction region, the front surface is convexlycurved to incline the front surface relative to the longitudinal axis ofthe shank, and the edge surfaces converge relative to each other towardsthe tip, whereby, on forcing the nail into the hoof, the reaction regionis adapted to produce a resultant force on the nail caused by engagementof the reaction region with the hoof, the resultant force being adaptedto further predispose the nail to bend about the rear surface of thereaction region.
 12. A nail according to claim 11, wherein the reactionregion merges with the remaining part of the shank such that theflattened profile extends towards the head.
 13. A nail according toclaim 1, wherein, in the reaction region, the edge surfaces are convexlycurved towards the tip so as to converge towards the tip, and the frontsurface is inclined relative to the centreline or longitudinal axis ofthe shank.
 14. A nail according to claim 13, wherein the reaction regionmerges with the remaining part of the shank such that the flattenedprofile extends towards the head.
 15. A nail according to claim 13,wherein said front surface is convexly curved, whereby, on forcing thenail into the hoof, the reaction region is adapted to produce aresultant force on the nail caused by engagement of the reaction regionwith the hoof, the resultant force being adapted to further predisposethe nail to bend about the rear surface of the reaction region.
 16. Anail according to claim 15, wherein the reaction region merges with theremaining part of the shank such that the flattened profile extendstowards the head.
 17. A method of forming a nail for fixing a shoe to ahoof, the nail having a head, and a shank extending along a longitudinalaxes from the head and terminating in a tip, the shank having aflattened profile having front and rear surfaces, and the methodincluding the steps of:(i) providing a nail blank formed from feedmaterial having a predominately uniform grain structure; (ii) locatingthe nail blank between cooperating dies at least one of which has arecess extending generally parallel to the longitudinal axis of theshank; (iii) forming the flattened profile of the shank by cold workingthe nail blank in a direction substantially transverse to thelongitudinal axis, with a front surface of the shank being subjected toa greater degree of cold working than a rear surface of the shank,wherein said cold working is effected by a pressing operation with thedies such that during the pressing, operation, metal tends to flow intosaid recess; and (iv) shearing the blank in the direction of thelongitudinal axis to remove the metal which has flowed into the recessand to form the opposing side surfaces of the shank which interconnectthe front and rear surfaces.
 18. A method according to claim 17 whereinthe sides of the nail blank interconnecting the front and rear surfacesare not constrained during the pressing operation.
 19. A methodaccording to claim 17 wherein said recess is one of a pair of recesseslocated on opposing sides of the blank.
 20. A method according to claim17 wherein the feed material is wire.
 21. A method according to claim 20including:(i) providing wire of a cross section of similar area to thesubsequent shank; (ii) upsetting an end of the wire to form the head;and (iii) working a nail blank cut from the wire and including the head,substantially without drawing the blank, to form the flattened profileof the shank, and forming the tip on the flattened shank.